EFFECTS OF VISCOELASTICITY OF BULK POLYMER-SOLUTION ON THE SURFACE-MODES AS PROBED BY LASER-LIGHT SCATTERING

The effects of surface tension, surface dilational modulus, stress rel axation time, and shear stress modulus on the surface laser light scat tering (SLLS) spectrum of polymer solutions are investigated. The capi llary wave component is significantly affected by both the stress rela xation time and the amplitude of the shear stress modulus. At moderate concentration, before crossing over to the elastic regime, a strong q uasielastic component dominates the SLLS spectrum in polymer solution. In the viscoelastic regime, the capillary wave component of the SLLS spectrum is suppressed by the increase of the surface dilational modul us. The decrease of the surface tension gives rise to an effect simila r to that caused by increasing the dilational modulus. However, at hig h polymer concentration in the elastic regime, the dilational modulus has only a negligible effect on the SLLS spectrum, in contrast to the effect of surface tension. (C) 1998 American Institute of Physics.